1. Field of the Invention
The invention relates to a drive device for machine auxiliary units.
2. Description of the Related Art
Machines, such as the internal combustion engine of a motor vehicle, usually have various associated machine auxiliary units, such as a generator for generating power, an air-conditioning unit, a power steering unit, a water pump etc. The internal combustion engine or other such machine typically employs a belt to drive the machine auxiliary units. More particularly, the crankshaft of the internal combustion engine has a belt pulley for driving the belt and the belt is coupled mechanically to belt pulleys of the machine auxiliary units. Therefore, the machine auxiliary units are rotated simultaneously and are driven by the belt as the internal combustion engine rotates.
The use of a belt to transmit a high torque from the machine to the machine auxiliary units can be difficult. A wider belt can be used to transmit a higher torque. However, a wider belt requires a corresponding amount of installation space to be available. The belt tension also can be increased to transmit the higher torque, but the higher tension subjects the bearings to higher loads. Interlocking belts, such as toothed belts, can be used, but are particularly disadvantageous if the coupled machine auxiliary unit is an electrical machine or a generator. More particularly, the high degree of inertia of the generator can subject the belt to a high level of loading due to rotary vibrations of the machine. This problem is particularly likely if the machine is an internal combustion engine that has a crankshaft to drive the belt.
DE 102 00 686 discloses using a poly-V-belt with corresponding belt pulleys for driving the machine auxiliary units by the crankshaft.
DE 1 107 033 discloses a combined V- and toothed belt. However, DE 1 107 033 explains only that the V-belt is suitable for transmitting considerable forces, whereas the toothed belt is provided to transmit precise control movements.
The object of the invention is to provide an alternative drive device for machine auxiliary units, of which at least one is an electrical machine.